Washington: More than 1.8 million dead Americans remain listed as active voters, according to a study which described the US voter registration system as "plagued with errors and inefficiencies."

The research conducted by the non-partisan Pew Center on the States also revealed that one in every eight voter records contains inaccuracies, and at least 51 million eligible voters are not registered to take part in elections.

The study comes as the US prepares for presidential and congressional elections in November.

"Voter registration is the gateway to participating in our democracy, but these antiquated, paper-based systems are plagued with errors and inefficiencies," said David Becker, director of Election Initiatives at Pew.

Of the approximately 24 million incorrect voter registrations across the country, or 13 percent of the national total, more than 1.8 million of those are for people who are deceased, the center found.

Another 2.75 million people are registered in more than one state. About 12 million records contain incorrect addresses, meaning either the voters have moved or the Postal Service would have trouble finding them, it said.

Some of the errors can be explained by the fact that one in eight Americans moved during the 2008 and 2010 election years, mainly young people and members of the US military.

A case study carried out in the northwestern US state of Oregon showed that every new voter registration cost USD7.67, as compared with just 35 cents per voter spent in Canada, which uses better technology to maintain voter lists.

The 51 million eligible voters who are not registered represents nearly a quarter of all eligible citizens. In Canada, 93 percent of the eligible population is registered, according to Pew.

The center said it was working with state election officials on ways to ensure greater accuracy including the cross-checking of voter lists with other data sources such as motor vehicle records and allowing voters to register online to minimise human error.